Which of the following is not the sponsor's responsibility concerning investigational products?

The sponsor's responsibilities in clinical trials are clearly outlined by regulatory authorities like the FDA. Among these responsibilities, maintaining accurate records of safety and effectiveness, reporting adverse events to the FDA, and ensuring that informed consent is obtained from participants are all pivotal roles that the sponsor must fulfill to ensure the integrity of the trial and the safety of the participants.

The maintenance of records pertaining to the receipt, use, and disposition of the investigational product is indeed an essential part of the trial process. However, this task is often delegated to other personnel or entities, such as the research institution or clinical site, which typically manage the day-to-day logistics of the trial. While the sponsor must ensure that these records are kept and report on them, the actual responsibility for logging every detail of the investigational product's handling often falls to the researchers or the site, making it slightly different in nature from the other aforementioned responsibilities, which directly involve the sponsor's oversight role in the protection of participants and the scientific integrity of the trial.

Therefore, the correct choice reflects a responsibility that is generally managed at the site level rather than being a direct, primary responsibility of the sponsor.